A circuit is known from US 2010/0277839 A1 which protects a switching circuit connected to it from an excessively high amplitude of a high-frequency signal. In this context, the circuit comprises a detection unit, which detects a high-frequency signal with an excessively high level, and a switch unit, which comprises PIN diodes (English: positive intrinsic negative diode; German: positiv intrinsische negative Diode), which limits the high-frequency signal dependent upon the result determined by the detection unit. The disadvantage with US 2010/0277839 A1 is that the circuit construction is complex and, with a detection unit and a switch unit, requires two different circuit stages. This active control circuit is also very complex because of the control transistors used and the generation of the supply voltages for the detector diodes and the control transistors.